Ruby on rails sdk location in Ubuntu

Hi people.

I want to use idea for ruby on rails development but can't seem to install the ruby on rails sdk.

I am running ubuntu.

I added a ruby sdk using the directory "/usr", and I can create and run ruby scripts no problem.

I can't seem to find the ruby on rails sdk though. I have installed it under "/usr/lib/ruby/gems/1.8/gems/rails-1.2.3" and it works because I have got it up and running using the command line.

I have tried adding all directory locations I can think of with no success.

On the screen cast I noticed it is using something called "InstantRails". I've had a look at this and it seems to be windows only.

Any idea if this is possible on ubuntu at the moment? and which directory should I use? and do I need to download anything else?

Thanks very much for any information, Paul.